The delivery of radio frequency (RF) energy to target regions within solid tissue is known for a variety of purposes of particular interest to the invention. In one particular application, RF energy may be delivered to diseased regions (e.g., tumors) for the purpose of ablating predictable volumes of tissue with minimal patient trauma.
RF ablation of tumors is currently performed using one of two core technologies. The first technology uses a single needle electrode, which when attached to a RF generator, emits RF energy from an exposed, uninsulated portion of the electrode. The second technology utilizes multiple needle electrodes, which have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. U.S. Pat. No. 6,379,353 discloses such a probe, referred to as a LeVeen Needle Electrode™, which comprises a cannula and an electrode deployment member reciprocatably mounted within the delivery cannula to alternately deploy an electrode array from the cannula and retract the electrode array within the cannula. Using either of the two technologies, the energy that is conveyed from the electrode(s) translates into ion agitation, which is converted into heat and induces cellular death via coagulation necrosis. The ablation probes of both technologies are typically designed to be percutaneously introduced into a patient in order to ablate the target tissue.
In the design of such ablation probes, which may be applicable to either of the two technologies, RF energy is often delivered to an electrode located on a distal end of the probe's shaft via the shaft itself. This delivery of RF energy requires the probe to be electrically insulated to prevent undesirable ablation of healthy tissue. In the case of a single needle electrode, all but the distal tip of the electrode is coated with electrically insulative material in order to focus the RF energy at the target tissue located adjacent the distal tip of the probe. In the case of a LeVeen Needle Electrode™, RF energy is conveyed to the needle electrodes through the inner electrode deployment member, and the outer cannula is coated with an electrically insulative material to prevent RF energy from being transversely conveyed from the inner electrode deployment member along the length of the probe.
When introducing an ablation probe within a patient to treat target tissue, it is desirable that the distal end of the ablation probe, where the RF energy will be directed, is in contact with the target tissue. This may be achieved by visualizing the ablation probe with an imaging device located outside the patient's body, such as an ultrasound imager. The echogenicity of the probe determines how efficiently and accurately the probe may be located using ultrasound techniques. That is, the more echogenetic the ablation probe, the easier it is to determine the location of the probe with ultrasound imaging and to ensure accurate contact with the target tissue.
While echogenicity of a probe may be desired, a user is nonetheless limited to the capabilities the probe has after it is manufactured and shipped. Thus, a probe lacking suitable echogenicity may not be easily visualized with an imaging device during a tissue ablation procedure, making the ablation procedure more difficult. In another situation, a user may obtain a probe from a manufacturer without expecting a need for having an echogenic probe, but changed circumstances may require additional echogenicity of the probe.
Therefore, there is a need in the art for a medical probe with increased echogenicity. There is also a need in the art for providing a user the capability of increasing the echogenicity of a probe after it has been manufactured and shipped.